The present inventions relate to transducer systems for emitting or detecting radiant energy, for example optical energy. The inventive concepts involve transducer systems utilizing principles of constructive occlusion as well as specific techniques for tailoring the performance characteristics of such systems.
Radiant energy transducers find a wide range of applications in modem technology. Electrically driven transducers, for example, emit radiation to illuminate a desired area or footprint. The transducer system may illuminate the area for a number of reasons. For example, if the emitting transducer emits visible light, the illumination may facilitate use of the area by human personnel. If the illumination of the area provides infrared radiant energy, the illumination may facilitate some associated detection operation or human monitoring of the area through special night vision equipment.
Other radiant energy transducers detect radiant energy from within a desired field of view and provide signals for further electrical processing. For example, a light detecting transducer may provide signals that a processor can analyze to determine the direction and/or intensity of incoming light. The processed information may represent a position of a reflective object or light source within the field of view. These are just a few examples of the applications of radiant energy transducer systems.
Different applications of radiant energy transducers require different transducer performance characteristics. For example, an illumination application might require that the transducer uniformly illuminate a flat surface of a specified area (the footprint) at a known distance and angle from the transducer with a specified radiation intensity. Typically, the specification for such an illuminating transducer would not specify the amount of radiation transmitted to areas outside the specified footprint. Simple radiation sources, such as light bulbs or lights with reflectors and/or lenses typically distribute a substantial amount of radiation outside the desired footprint. This reduces efficiency. Stated another way, to achieve the desired illumination intensity within the footprint, the power applied to the transducer must be relatively large in order to allow for the energy lost to areas outside the desired footprint. Also, such a system often over radiates a portion of the desired footprint.
Similar problems arise in radiant energy detecting transducers. To insure adequate sensitivity to energy from within the field of view, the transducer typically will receive additional radiant energy from outside the desired field of view. Also, it often is difficult to maintain uniform sensitivity over the entire field of view.
Prior attempts to address these problems have involved complex arrangements of lenses and reflectors. Such arrangements make transducer manufacture expensive. Such arrangements also are subject to problems of misalignment and raise concerns about the durability and ruggedness, in applications outside of laboratory conditions.
A need therefore exists for radiant energy transducer systems, e.g. emitters and detectors, having high efficiency and desired operational characteristics for specific applications. The transducer systems should be relatively easy to manufacture and therefore relatively inexpensive. Also, there is a need for transducers of this type that are relatively rugged and durable, when used in real applications.
Applicants have developed a number of radiant energy transducer systems, which reduce some of the above noted problems, based on a theory of beneficial masking referred to as xe2x80x98Constructive Occlusionxe2x80x99. Constructive Occlusion type transducer systems utilize an electrical/optical transducer optically coupled to an active area of the system. The systems utilize diffusely reflective surfaces, such that the active area exhibits a substantially Lambertian characteristic. For example, the active area may comprise a diffusely reflective cavity formed in a base. A mask occludes a portion of the active area of the system, in the example, the aperture of the cavity, in such a manner as to achieve a desired response characteristic for the system.
For example, in a series of prior related cases, applicants disclosed cavity and mask based transducer systems that provide uniform response characteristics (e.g. emission energy for light distributors or sensitivity for detectors) over a wide range of angles relative to the transducer system. The prior Constructive Occlusion cases include U.S. Pat. Nos. 5,705,804, 5,773,819, 5,733,028 and 5,914,487, the disclosures of which are incorporated entirely herein by reference.
Applicants"" prior Constructive Occlusion type transducer systems have allowed considerable tailoring of the optical/electrical performance characteristics of radiant energy transducing systems. However, some desired applications require still further enhancements to achieve the desired system characteristics, and a need still exists to further increase the efficiency of the transducer systems. For example, a need still exists for a transducer system of even higher efficiency exhibiting uniform performance over a designated planar surface.
The objective of the invention is to produce a radiant energy transducer system having a tailored intensity characteristic over a desired footprint or field of view.
Another objective is to maintain a relatively high efficiency of the transducer characteristic over the footprint or field of view.
One more specific objective is to provide a transducer having a planar uniformity of response or illumination over a desired footprint.
The inventive concepts involve a series of xe2x80x98tailoringxe2x80x99 techniques, which enable the system designer to adapt a transducer system to a specific illumination or detection application requiring a particular performance. One of these techniques utilizes the principles of constructive occlusion, with selection of the optical parameters of the constructive occlusion system, to satisfy the performance demands of the particular application. Constructive occlusion utilizes a mask sized and positioned to occlude a substantial portion of an active optical area, such as an aperture of a diffusely reflective cavity, in such a manner as to provide the desired performance characteristic.
Constructive occlusion of this type may be used alone or in combination with several other techniques. One additional mechanism used to further tailor performance involves a non-diffuse reflective shoulder (specular or retro-reflective) around a peripheral section of the mask and cavity type transducer system. Another technique involves using a retro-reflector along a portion of the periphery of the system, to limit the angular field of view and to redirect certain light back into the system for further optical processing.
Another technique, used with a mask and cavity type constructive occlusion system, involves use of one or more reflective walls along one side of the system. The reflective walls limit the field of view to angles on the opposite side of the axis or plane of the walls.
These techniques enable a system designer to adapt the transducer system to a wide range of applications. A lighting system, for example, may uniformly illuminate a distant planar surface, such as a desktop or a section of a floor or ceiling. The resulting transducer systems are relatively simple in structure, making them easy to manufacture and rugged.
The present invention uses materials having a variety of different types of types of reflectivity. Recall for example that a material providing a diffuse reflectivity reflects light, impacting at an incident angle to the surface, over a range of angles of reflection, i.e. in many different directions. A material providing a specular reflectivity reflects light impacting at an incident angle to the surface in a new direction, but the angle of reflection relative to the surface equals the angle of incidence. A material or surface providing a retro-reflectivity reflects light back along the same path on which it arrived or on a closely parallel path.
In one aspect, the invention relates to a radiant energy transducing system. This system comprises a base, a mask and an electromagnetic transducer. The base has a diffuse active optical area. The mask is spaced from the base and positioned to occlude a portion of the active optical area. The transducer provides a conversion between radiation associated with the active optical area and corresponding electrical signals. The mask has a size in relation to the active optical area and is spaced a distance from the active optical area such that the system exhibits a predetermined performance characteristic over a field of view.
In this first aspect, the system further includes a shoulder adjacent to and extending outward from a peripheral section of the active optical area. The shoulder has a surface facing the field of view, and the shoulder surface has a non-diffuse reflective characteristic. Disclosed examples utilize a specular shoulder surface or a retro-reflective shoulder surface.
Examples of such a system disclosed in detail below utilize transducers which may be sources emitting radiant energy or use transducers which may be sensors/detectors for converting received radiant energy to electrical signals. In many of the preferred embodiments, the active optical area relates to the aperture of a diffusely reflective cavity. The cavity may be formed in the base or the mask. If in the base, for example, the periphery of the aperture defines the active area. If formed in the mask surface facing the base, the reflection of the aperture onto the base may be considered as the active area. The transducer is coupled to process radiant energy within the cavity and the associated active area, for example, to emit light through a fiber into the cavity for emission via the aperture.
In a mask and cavity type transducer system in accord with this aspect of the invention, the mask height above the aperture and the relationship of the size of the mask to the size of the aperture are the principal factors effecting the sensitivity or illumination intensity distribution within the field of view or over the desired footprint area. The shape of the mask and aperture also has have some impact on distribution. The shape of the aperture and the shape of the corresponding mask are the principal factors effecting the shape of the field of view or footprint, although mask height and the relative sizes of the mask and aperture may have some impact. The width of the shoulder and the particular reflectivity effect the performance characteristics in certain sections of the field of view.
In another aspect, the invention relates to a radiant energy transducing system including a base, a mask, a transducer and a retro-reflective ring. The base, mask and transducer in this system are essentially similar to those discussed above relative to the first aspect of the invention. Some embodiments include a shoulder adjacent to and extending outward from a peripheral section of the active optical area. The ring, in this system, is located along a periphery of this shoulder. The ring extends from the shoulder toward the field of view. Alternative embodiments locate a retro-reflector at other positions around the system for example, opposite the base and across the system axis. The retro-reflector or ring serves to limit the field of view. The retro-reflective surface faces toward the mask and the active optical area, for reflecting radiant energy diffused from those elements at angles outside the field of view back toward the mask and optical area, for further optical processing.
The shape of the wall of the retro-reflector also may be selected to facilitate a particular application. The retro-reflector, for example, may extend straight out from the shoulder or other wall. Other embodiments of the retro-reflector may curve, bend or slant inward toward the axis of the system. Such wall shapes enable the retro-reflector to limit the angle of view as desired with less height out from the shoulder, when compared to the straight wall. These shapes also provide a lesser angle of incidence of light on the retro-reflective surface of the wall, which enables the use of retro-reflective materials, such as retro-reflective paints or tapes, which may have a smaller angle of acceptance. For other applications, it may be desirable to angle the retro-reflector outwards, away from the other system elements.
The principles of the retro-reflector may have application separate and apart from their use with constructive occlusion. Thus, another aspect of the invention relates to a system for emitting radiant energy, comprising a source, a distributor and a retro-reflector. The distributor is coupled to the radiant energy source, for distributing the radiant energy from the source with a desired intensity distribution pattern. The retro-reflector is spaced a predetermined distance from the distributor and positioned to reflect a portion the radiant energy from the distributor, that would be outside of a desired field of view of the system, back to the distributor. This retro-reflection enables distribution of the recycled energy, in the desired distribution pattern, as part of the energy emitted within the desired field of view.
Another aspect of the invention, relating to tailoring of the performance characteristics of a mask and cavity type constructive occlusion transducer system, utilizes a reflective wall to optically xe2x80x98cut-offxe2x80x99 a portion of the system and reflectively image the system to act much like a full symmetrical system if observed from within the field of view.
In this aspect, the invention is a system comprising a base, a mask and a transducer. The base has a diffuse active optical area, which faces substantially toward at least a portion of an intended field of view of the system. A shoulder, adjacent to the periphery of the active optical area, has a reflective surface facing the field of view. The mask is spaced from the base and positioned to occlude a portion of the active optical area of the base. The mask has a reflective surface facing substantially toward the active optical area of the base. In this aspect of the invention, the system includes a diffusely reflective cavity. Specific embodiments are disclosed with the cavity formed in the active optical area of the base, for example, so that the aperture of the cavity defines the active optical area. Other specific embodiments have the cavity formed in the facing surface of the mask.
Systems in accord with this aspect of the invention also include a reflective wall, which extends from a side of the cavity substantially to an edge of the other one of the active optical area of the base and the surface of the mask. For example, if the cavity is in the base, this wall extends to the facing surface of the mask. If the cavity resides in the mask, the wall extends to the active area of the base. Another reflective wall extends from a periphery of the mask away from the base. In some preferred embodiments, these walls actually are coplanar, but in others they are offset, for example at opposite edges of the mask.
The radiant energy transducer provides conversion between radiation associated with the active optical area and corresponding electrical signals. The mask has a size in relation to the active optical area and is spaced a distance from the active optical area such that the system exhibits a predetermined performance characteristic with respect to the radiant energy over the intended field of view.
The reflective walls substantially limit the field of view to one side of the axis of the aperture. Considered another way, however, these walls serve to substantially form a mirror image of the system components. Consequently, the system exhibits a performance to one side of the walls in a manner similar to an entirely symmetrical system, but with substantially increased performance over the limited field of operation.
A variety of different system embodiments may utilize the xe2x80x98cut-offxe2x80x99 technique alone or in combination with other tailoring techniques disclosed herein. For example, a cut-off system may have a specular shoulder. Also, the cut-off system may include a retro-reflector. The retro-reflector may be along a periphery of the shoulder. In one embodiment, however, the retro-reflector is along a periphery of one of the reflective walls, preferably opposite the cavity formed in the base.
The transducer systems of the invention can provide a wide range of performance characteristics, to meet the demands of different applications. These systems, for example, can provide emission or response characteristics that are substantially uniform with respect to angle relative to the system axis, over a range of angles. A number of significant applications, particularly for radiation emission systems, provide uniform performance over a planar footprint.
Thus, another inventive concept relates to a radiant energy emission system providing planar uniformity. This system includes a radiant energy source, a base and a mask. In this case, the base has a diffusely reflective active optical area, for reflecting and diffusing the radiant energy. The source is optically coupled to the active optical area of the base. The mask is spaced from the base and positioned so as to occlude a portion of the active optical area. The configuration of the base and the mask produces an illumination over a predetermined planar footprint. The size and positional relationship of the mask to the active area results in a substantially uniform illumination over the planar footprint.
The transducer system providing planar uniformity can incorporate various combinations of the other features described above, to improve efficiency and/or to tailor the field of view. For example, the system may include a specular shoulder area and/or a retro-reflective ring. Another disclosed embodiment providing planar uniformity utilizes the specular reflective wall, to limit the field of view or footprint to one side of the system. This later system may be mounted with that wall against a flat surface, such as a building wall or ceiling, to illuminate a plane perpendicular to the flat surface.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.